This invention relates to a method and apparatus for detecting leaks in fluid pressurized vessels, the most typical being a pipeline. More particularly, this invention relates to an electronic instrument and method of operation thereof, which can detect the rate of change of pressure or flow and total pressure or flow change caused by a break or leak in a pipeline carrying a liquid or gas, and take remedial measures therefor.
Fluids such as natural gas, oil or the like, are often transported over long distances by pipeline. It is often important to quickly detect leaks or breaks in the pipeline, not only for a conservation of the fluid, but also in the case of flammable, toxic or like fluids, for safety purposes. A break or leak is most often characterized by a pressure drop over a period of time with some pressure drops being rapid and others being quite slow. The prior art is characterized by a number of devices which attempt to detect the leak by monitoring this pressure change. For example, U.S. Pat. Nos. 2,836,192 and 2,915,042 are typical mechanical/pneumatic devices designed for that purpose. These types of devices are usually only workable with gas lines as opposed to liquid lines and can have certain drawbacks even when operating on gas lines. For example, these devices often fail to detect small rates of pressure change, which, if existing over a long period of time, must be detected. Then too, these devices are susceptible to failure due to the plugging of orifices, condensation in the rate tanks which changes the volume thereof, and corrosion of the various parts, the latter occurring when the pipeline is carrying a caustic or sour gas.
Some electronic devices have been developed in an attempt to avoid the aforementioned problems. These devices can satisfactorily detect changes in pressure over a period of time and if a greater pressure rate of change is detected than a preselected amount, remedial measures can be taken. However, if a change in pressure greater than the preselected amount occurs, followed by a period of relative pressure stability, followed again by a change in pressure greater than the preselected amount, etc., the total pressure drop would be indicative of a problem in the pipeline but would go undetected by this device. Similarly, fluctuations in line pressure, not resulting in an appreciable pressure change could falsely activate these prior art devices.
Other systems for detecting leaks or breaks in pipelines have been directed to detecting variations in the intensity of the sound of the flowing gas. These devices have met with little success in that background noises are indistinquishable thus often causing false alerts. In addition, like the other prior art discussed above, these systems are not applicable to liquids where a surge or large instantaneous rate of pressure drop exists upon a break.
Additionally, none of the prior art of which I am aware provides the additional feature of a means to shut down the system under inordinately low or high pressure situations whether or not a break is indicated.